Nature of Business and Summary of Significant Accounting Policies - Number of Shares Outstanding for Calculation of Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Basic net loss and loss per share, Numerator (Loss)	$ (11,589)	$ 3,036	$ 5,486	$ 38	$ (51,172)	$ 5,826	$ 4,037	$ 3,055	$ (3,029)	$ (38,218)	$ (5,602)
Diluted net loss and loss per share, Numerator (Loss)									$ (3,029)	$ (38,218)	$ (5,602)
Basic net loss and loss per share, Denominator (Shares)									34,445,256	33,979,549	28,791,662
Diluted net loss and loss per share Denominator (Shares)									34,445,256	33,979,549	28,791,662
Basic net loss and loss per share, Per Share Amount	$ (0.34)	$ 0.09	$ 0.16	$ 0.00	$ (1.49)	$ 0.17	$ 0.12	$ 0.09	$ (0.09)	$ (1.12)	$ (0.19)
Diluted net loss and loss per share, Per Share Amount	$ (0.34)	$ 0.09	$ 0.16	$ 0.00	$ (1.49)	$ 0.17	$ 0.12	$ 0.09	$ (0.09)	$ (1.12)	$ (0.19)